Device and method for the high-frequency etching of a substrate using a plasma etching installation and device and method for igniting a plasma and for pulsing the plasma out put or adjusting the same upwards

ABSTRACT

A device and a method capable of being carried out therewith for, preferably, anisotropically etching a substrate ( 10 ), in particular, a patterned silicon body, with the assistance of a plasma ( 14 ), is proposed. In the process, the plasma ( 14 ) is produced by a plasma source ( 13 ) to which a high-frequency generator ( 17 ) is connected for applying a high-frequency power. Moreover, this high-frequency generator is in communication with a first means which periodically changes the high-frequency power applied to the plasma source ( 13 ). Besides, provision is preferably made for a second means which adapts the output impedance of the high-frequency generator ( 17 ) to the prevailing impedance of the plasma source ( 13 ) which changes as a function of the high-frequency power. The proposed anisotropic etching method is carried out in separate and alternating etching and polymerization steps, a higher high-frequency power of up to 5000 watts being, at least temporarily, applied to the plasma source ( 13 ) during the etching steps than during the deposition steps. The proposed device is also suitable for igniting a plasma ( 14 ) and for adjusting upward or pulsing a plasma power from a starting value to up to 5000 watts.

FIELD OF THE INVENTION

The present invention relates to a device and a method for high-rateetching a substrate, in particular, in an anisotropic manner, using aplasma etching system, it being possible to achieve periodically varyingplasma powers of up to 5000 watts as well as to a device and a methodfor igniting a plasma and to adjusting upward or pulsing the plasmapower according to the species defined in the independent claims.

DESCRIPTION OF RELATED ART

German Patent 42 41 045 C1 describes a method for anisotropicallyetching silicon using high etching rates and high mask selectivity, ahigh-density plasma source having preferably inductive high-frequencyexcitation being used for liberating fluor radicals from afluor-delivering etching gas and (CF₂)_(x)-radicals from a passivatinggas delivering Teflon-forming monomers. In the process, etching gas andpassivating gas are used alternatingly, a side wall polymer film beingbuilt up on the side walls of already etched patterns during thepassivation steps or polymerization steps, the side wall polymer film,during the per se isotropic etching steps, each time being partiallyremoved again with the assistance of ions and, at the same time, thesilicon pattern ground being etched by fluor radicals. This processrequires a high-density plasma source which also generates a relativelyhigh density of ions (10¹⁰-10¹¹ cm⁻³) of low energy.

An increase in the etching rate, which is required for manyapplications, is generally to be expected when the high-frequency powercoupled into the plasma is increased.

In methods as described in German Patent 42 41 045 C1, however, this issurprisingly not the case. Instead, it is observed that the etching ratein silicon increases only slightly in response to increasing the powerof the plasma source while, at the same time, unwanted profiledeviations, in particular, in the upper third of the produced trenches,greatly increase, resulting in profile indentations or undercuts of themask edge.

These effects, on one hand, originate from unwanted capacitiveinterferences from regions of the inductive plasma source, which carryvery high high-frequency voltages. When working with higher powers andvoltages, these unwanted interference effects are naturally higher aswell.

In so far as the plasma source itself is affected, the mentioned effectscan be rectified at least to a great extent by advanced feed concepts ofthe plasma source and, for example, by using a special aperture as isdescribed in German Patent 197 34 278 C1. However, those profiledeteriorations which are due to the process and therefore have to betackled from the process side remain.

While in simple plasma patterning processes, an increase in the plasmapower, because of the resulting increased production of ions and etchingspecies, gives rise to the desired increase in the etching rate, in thecase of the method according to German Patent 42 41 045 C1, thedeposition steps must also be taken into account in addition to theetching steps. In this context, an increase in the plasma power duringthe etching steps not only results in the desired increased productionof etching species and ions but also changes the deposition steps in acharacteristic manner.

A very important aspect of German Patent 42 41 045 C1 is the side wallfilm transport mechanism which, during the per se isotropic etchingsteps, assures that the side wall protective film is also moved into thedepth of the trench during further etching and that it can provide localedge protection already there. However, during the deposition orpolymerization steps themselves, such a transport mechanism is onlydesired within certain limits. Thus, the intention is, in particular, toprevent that excessive side wall polymer is driven down into thetrenches already during the deposition cycles and that it is thenlacking above, i.e., the side wall film gets too thin there.

If the plasma power is increased during the etching and depositionsteps, for example, in the case of a process according to German Patent42 41 045 C1, an increased polymer transport from the side wall into thedepth of the trenches takes place, per se unintentionally, also duringthe deposition steps in competition to the coating of the side wallssince, above a certain plasma power, the deposition rate can no longerbe substantially increased but, instead, ions are increasingly producedwhich impinge on the substrate to be etched.

Due to the plasma potential which lies somewhat above the substratepotential even without an additionally applied substrate electrodevoltage, this increasing ion flux toward the substrate results in thatan increasing part of the deposited film material is pushed into thedepth of the trenches and to the etching ground already during thedeposition steps. In particular, the plasma has a plasma potential ofseveral Volts up to several 10 Volts with respect to grounded surfacesand, consequently, also with respect to a substrate on the substrateelectrode, which is tantamount to a corresponding ion accelerationtoward the wafer. Therefore, an increased ion density also signifies anincreased ion action upon the substrate surface and, in particular, uponthe trench side walls although, explicitly, no ion acceleration voltageis applied to the substrates.

As a result of the explained polymer removal and carrying over into thedepth of the trenches already during the deposition steps in the case ofvery high plasma powers, the polymer material needed for the side wallprotection in the subsequent etching steps is finally lacking in theupper parts of the etched trenches when working with high plasma powers,which manifests itself in the mentioned profile deviations more or lessin the upper third of the trench profile. At the same time, the polymermaterial transported to the etching ground in excess also disturbs theetch removal during the subsequent etching steps and, on the whole,leads to the observed saturation of the etching rate in spite of thefurther power increase in the source. A further effect in thisconnection is the “hardening” of the deposited polymer material whenworking with very high power densities, i.e., an increased carboncontent in polymers compacted in this manner, which makes the subsequentpolymer removal more difficult and, consequently, reduces the etchingrates.

SUMMARY OF THE INVENTION

Therefore, it is an object of the present invention to overcome asaturation of the etching rate in spite of a higher high-frequency powerprovided by the plasma source, thus drastically increasing the etchingrate. A further object of the present invention is to enable theignition and the coupling in of very high high-frequency powers into a,in particular, inductive plasma source in a stable manner.

The devices according to the present invention and the methods accordingto the present invention having the characterizing features of theindependent claims have the advantage over the background art that theyallow the high-frequency power applied to a plasma source to beperiodically changed so that, for example, alternating deposition orpolymerization and etching steps can be carried out very advantageouslyusing high-frequency powers of different magnitude. In this context, ahigher high-frequency power is in each instance very advantageouslyapplied to the plasma source during the etching steps than during thedeposition steps.

Moreover, using the device for etching according to the presentinvention and the method for anisotropically etching a substrateaccording to the present invention, considerably higher etching ratescan be achieved than with known etching methods and etching devices. Inthis context, the difficulty existing in known methods heretofore that,in spite of a continuous increase in the plasma power, a saturation ofthe etching rate occurs in anisotropic etching methods where depositionsteps and etching steps are used alternatingly.

Furthermore, it is very advantageous that the device according to thepresent invention and the method for igniting and adjusting upward aplasma carried out therewith, for the first time, allow very highhigh-frequency powers to be coupled into a, in particular, inductiveplasma source in a stable manner.

Advantageous embodiments of the present invention are derived from themeasures specified in the subclaims.

Thus, the method according to the present invention allows the methodaccording to German Patent 42 41 045 C1 to be considerably improved in avery advantageous manner by applying a low plasma power during thedeposition steps and by applying a very high plasma power during theetching steps, extremely high etching rates being attained, for example,in silicon while retaining the advantages known from German Patent 42 41045 C1. In the etching method according to the present invention, inparticular, the deposition steps very advantageously remain nearlyunchanged. Moreover, the etching steps are advantageously carried outusing very high plasma powers of up to 5000 watts at preferablyincreased SF_(6/O) ₂ flow and preferably increased process pressure.

Besides, the uniformity of the etching process is significantly improvedby switching back the high-frequency power, according to the presentinvention, during the polymerization steps so that the substrate centerand the substrate edge have nearly identical etching rates. This istrue, in particular, if the method for high-rate etching according tothe present invention is combined with an aperture device in the plasmaetching system as is known from German Patent 197 34 278. A veryparticularly advantageous variant of the method according to the presentinvention with regard to the uniformity of the etching over a waferresults if a plasma etching system as is known, for example, from GermanPatent 197 34 278 is further operated using a symmetrically fed plasmasource as is proposed in German Application 199 00 179.

Moreover, the device for etching a substrate according to the presentinvention allows very high high-frequency powers of up to 5000 watts tobe coupled into, in particular, inductive plasma sources in a stablemanner. To this end, provision is advantageously made for a secondmeans, in particular, for an automated impedance transformer which iscontrolled in a manner corresponding to the variation in thehigh-frequency power of the plasma source. Besides, the speed-adaptedvariation in power of the plasma source or of the high-frequencygenerator feeding the plasma source, respectively, is at the same timeachieved in an advantageous manner via a ramp generator.

In this context, controlling the plasma power using a high-frequencygenerator and a ramp generator being in communication therewith as wellas an impedance transformer for adapting the impedance, in particular,in a continuous and automated manner, is very advantageously suitableboth for igniting and for adjusting upward a plasma up to highest powervalues and for alternating the power parameters at the plasma sourcebetween etching and deposition steps according to the present invention.

The increased formation of etching species through a higher plasma powercan further be promoted in an advantageous manner by increasing the flowof the fluor-delivering etching gas, for example, SF₆ simultaneouslywith the increase in power. In this case, to prevent sulfur depositionsin the exhaust area of the etching system, the oxygen content is to beadvantageously adjusted correspondingly. A further expedient way ofincreasing the production of fluor radicals concurrently with the powerincrease during the etching steps is increasing the process pressure. Inthis manner, fluor radicals are increasingly produced in the etchingplasma in place of additional ions, thus increasing the ratio of thenumber of fluor radicals to the ion density. The exceeding of a certainion density in the case of very high plasma powers is a disadvantage.

Besides, the power is advantageously not increased to, for example, morethan 1500 watts during the deposition or polymerization steps. Since thedeposition rate on the substrate suffices already when working with arelatively small power of 400 watts to 800 watts, an increase in powerof the plasma source during the deposition steps combined with otherwiseunchanged plasma etching parameters would, in any case, yield only fewadditional deposition species or would excessively compact the depositedpolymer and lead to a carbon concentration in the polymer. Moreover, bymaintaining the original small power of up to 1500 watts during thedeposition process, it is, at the same time, advantageously avoided thatthe ion density and, consequently, the ion action upon the substrate areincreased during the deposition steps. Because of this, the explaineddetrimental consequences of an increased ion density during thedeposition steps do no occur.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is explained in greater detail on the basis of thedrawing and in the following description.

FIG. 1 shows a plasma etching system having add-on parts;

FIG. 2 shows a first RC circuit used in an analog ramp generator;

FIG. 3 shows a second RC circuit having a diode; and

FIG. 4 shows a third RC circuit having two diodes.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a plasma etching system 5 having a substrate 10, inparticular, a patterned silicon wafer, which is to be provided withtrenches in an anisotropic plasma etching method, and having a substrateelectrode 11, a high-frequency a.c. voltage being applied, via asubstrate voltage generator 12, to substrate electrode 11 and, via thesubstrate electrode, also to substrate 10. Moreover, provision is madefor a plasma source 13 in the form of an inductive plasma source (ICPcoil), known per se, which, together with an introduced reactive gasmixture, produces a plasma 14 in a reactor 15. To this end, ahigh-frequency electromagnetic alternating field is generated via ahigh-frequency generator 17, the reactive gas mixture being exposed tothe electromagnetic alternating field. An arrangement of that kind isknown, for example, from German Patent 197 34 278 C1. In FIG. 1,moreover, provision is made for high-frequency generator 17 to be incommunication with a component 18 incorporating a ramp generator 19, andfor high-frequency generator 17 and plasma source 13 to be incommunication via an impedance transformer 16 (“matchbox”) known fromthe background art. The function and design of such a “matchbox” areknown per se. A particularly advantageous embodiment of the “matchbox”in connection with an inductive plasma source having balanced coil powersupply is described in unpublished German Application 199 00 179.5.

Using plasma etching system 5, for example, an anisoptropic etchingprocess including alternating etching and deposition steps is thencarried out as is described, for example, in German Patent 197 34 278 C1or, in particular, in German Patent 42 41 045 C1, the high-frequencypower applied to plasma source 13 being changed periodically.

To this end, initially, high-frequency powers of 400 watts up a maximumof 1500 watts, preferably from 600 watts to 800 watts are applied toinductive plasma source 13 during the deposition steps. In the process,the process pressure lies between 5 mTorr to 100 mTorr, for example, at20 mTorr.

The gas flow for the octafluorocyclobutane (C₄F₈) or hexafluoropropene(C₃F₆) used as passivating gas in the discussed example is 30 sccm to200 sccm, preferably 100 sccm. The duration of a deposition step is 1second to 1 minute, for example, 5 seconds.

During the etching steps following the deposition steps, high-frequencypowers of 600 watts to 5000 watts, preferably of 3000 watts, are appliedto inductive plasma source 13. In the process, the process pressure liesbetween 5 mTorr and 100 mTorr, for example, at 30 mTorr or 50 mTorr, andis preferably increased in comparison with the process pressure duringthe deposition steps. In the case of the etching gas SF₆ used in thediscussed example, the used gas flows are 100 sccm to 500 sccm,preferably, 200 sccm to 300 sccm, oxygen being added to etching gas SF₆in a proportion of 10 to 20 percent, preferably 15% in a manner knownper se to prevent sulfur depositions in the exhaust area of etchingsystem 5.

During the etching steps, moreover, a high-frequency power of 1 watt to50 watts is applied to substrate electrode 11 to accelerate ionsgenerated in plasma 14 toward substrate 10. In the discussed example,this high-frequency power is 8 watts in the case of a customary6″-silicon wafer as substrate 10. According to the specifichigh-frequency power, moreover, an ion acceleration voltage of 1 V to 50V, for example, of 15 V, is applied to substrate electrode 11. Theduration of the etching step is approximately 3 seconds up to 2 minutes.In the discussed example, the duration is approximately 10 seconds.

The application of very high powers of up to 5000 watts to inductiveplasma source 13 is technically very problematic since the plasmaimpedance changes in the measure in which the power is increased atplasma source 13. This is because an increasing electron and ion densityis produced in plasma 14 as the plasma power, i.e., the excitation ofplasma 14, increases. With the higher electron and ion density, however,plasma 14 increasingly has a lower impedance as seen from 40 plasmasource 13, i.e., the ideal state given in the case of high-densityplasmas, the “short-circuit case”, is more and more approached. Thismeans at the same time that the adaptation conditions of inductiveplasma source 13 to high-frequency generator 17, which usually has afixed output impedance of mostly 50 Ω, change, namely dynamically withincreasing power. Therefore, the output impedance of high-frequencygenerator 17 needs to be adapted to the impedance of inductive plasmasource 13 which essentially depends on the produced charge carrierdensity in plasma 14.

In the discussed example, impedance transformer 16 (“matchbox”) isprovided for that purpose. This impedance transformer 16, usually byautomatically and continuously or stepwise varying two variablecapacitors which constitute a capacitive transformer (voltage divider),guarantees that plasma 14 or plasma source 13, respectively, are alwaysoptimally adapted, in terms of their impedance, to high-frequencygenerator 17 and its high-frequency power. If this adaptation is notcorrect, reflected powers of up to 100 percent of the high-frequencypower input occur which return into high-frequency generator 17, andthere usually adjust back the forward power to prevent the generatoroutput stage from being destructed. In the case of the plasma powers ofup to 5000 watts used in the discussed example, this impedanceadaptation is necessarily carried out dynamically.

Thus, for igniting plasma 14, the impedance transformer is initiallybrought into a so-called “preset” position which, up to a certain lowplasma power, corresponds to the optimum “burning position” of impedancetransformer 16, i.e., the position of impedance transformer 16 in thestate “plasma on, low power”. In this case, the automatic control ofimpedance transformer 16 must take over only a fine control tocompensate for small tolerances of the plasma impedance. However, if theplasma power subsequently increases to values of, for example, more than1000 watts, as used in the discussed example during the etching steps orwhile the plasma power is adjusted upward upon ignition, the plasmaimpedance changes significantly. Thus, for example, with 3000 wattshigh-frequency power coupled in at inductive plasma source 13, theadjustment of impedance transformer 16 is significantly different fromthe ignition position or the position with low plasma power.

The equivalent applies when the plasma power is switched from a lower toa markedly higher value during the transition from a deposition step toan etching step such as in the present example. The sudden powervariation requires a corresponding correction at impedance transformer16. If this correction is not carried out fast enough, the forward poweron the generator side is abruptly reduced by corresponding protectivecircuits and, consequently, plasma 14 is temporarily extinguished orconstantly blinks.

In a preferred embodiment of the present invention, the explaineddifficulties during the ignition and adjusting upward of a plasma 14 inthe case of plasma powers between 800 watts and 5000 watts as well asthe periodic changeover of the plasma power, for example, betweendeposition steps and etching steps are solved in the discussed examplein that the power of high-frequency generator 17 is increased“adiabatically”, i.e., continuously or stepwise using a rate of risewhich can be dynamically corrected by impedance transformer 16. In thediscussed example, this means that the plasma power, for example, duringthe transition from a deposition step to an etching step, is increasedin a slowed down manner while, at the same time, impedance transformer16 continuously adapts to or corrects the changing impedance conditionson the basis of the changing plasma conditions.

In the concrete case of the plasma ignition, this manifests itself asfollows: impedance transformer 16 is in the preselected ignitionposition and high-frequency generator 17 begins to adjust upward itspower output continuously or stepwise in small steps from a preselectedstarting value to a target value. Plasma 14 will then ignite at acertain power, for example, 400 watts so that a defined impedance ispresent at plasma source 13. While high-frequency generator 17 thenfurther increases its power output, more and more charge carriers areproduced in plasma 14 and, consequently, the plasma or source impedanceis changed. Impedance transformer 16 allows for these changes byensuring the correct impedance transformation continuously andautomatically, for example, in a manner known per se by adjustingvariable capacitors. Thus, in the measure in which the generator poweroutput increases, impedance transformer 16 automatically and asconcurrently as possible adapts its adjustment at least temporarily tothe resulting plasma conditions. In this manner, it is therefore alsopossible for plasma powers of several kilowatts, in particular, up to5000 watts to be coupled into plasma 14 in a stable manner.

In the discussed example, typical values for the starting value lie atapproximately 0 to 400 watts whereas the target value is usually 800watts to 5000 watts. The time required for increasing the power betweenstarting and target values typically lies at 0.2 sec to 5 sec inparticular, 0.5 sec to 2 sec.

In the discussed example, it is essential that, at least during powerincreases, no sudden changes in the power of high-frequency generator 17occur which cannot be corrected by impedance transformer 16 but, ifpossible, all power changes be adapted to the correction rate ofimpedance transformer 16.

This also applies, in particular, to the alternation of the plasma poweraccording to the present invention from a low value during thedeposition steps to a very high value, preferably in the kilowatt range,during the etching steps. In this context, the deposition step with itsrelatively little power is initially uncritical. If now the change tothe etching step takes place, the generator slowly adjusts upward itspower output until, for example, after 2 seconds, the full generatorpower desired in the etching step is applied to plasma source 13. In thecase of such a rate of rise, customary impedance transformers can easilycorrect the adjustment correspondingly.

During the change into the deposition step, the plasma power can bereduced to the lower power value, which is desired in the depositionsteps, either suddenly or preferably also “adiabatically”, i.e. in aslowed down manner and adapted to the correction rate of impedancetransformer 16. Since the power during the deposition steps isuncritically low, however, both options are available here.

In the discussed example, the “adiabatic” control of the power ofhigh-frequency generator 17 can be carried out either stepwise in smallsteps or continuously. To this end, for example, in component 18, adigital ramp generator is programmed in a software-controlled mannerwhich is known per se or an analog ramp generator 19, also known per se,is incorporated in component 18, thus being interconnected between thesetpoint value output of a power control which, for example, isincorporated in component 18, and the setpoint value input ofhigh-frequency generator 17.

Software control or the digital ramp generator are recommendableespecially if the power of the high-frequency generator is requestedusing a digital command, for example, via a serial interface (RS232) asis the case with many known etching systems. In this case, the power ofhigh-frequency generator 17 must be adjusted upward in small steps,starting from a starting value up to the desired target value, by aseries of digital commands.

The analog variant via analog ramp generator 19 between the output ofthe system control and a generator setpoint value input is recommendableespecially if high-frequency generator 17 is controlled using an analogsignal, for example, a level value between 0 V and 10 V.

The simplest version of an analog ramp generator 19 is an RC circuit 23shown in FIG. 2, having a time constant which is adapted according tothe desired rate of rise of the power of high-frequency generator 17.This first RC circuit has a delaying effect both in the upward anddownward directions.

If the intention is for ramp generator 19 to be active only in theupward direction, i.e., only during power increase, but a desireddecrease in the power of high-frequency generator 17 is intended tooccur immediately, i.e. instantly, preferably, a second RC circuit 24provided with a diode as is shown in FIG. 3 is used.

If two freely selectable delay values are desirable for adjusting upwardand adjusting downward the power of high-frequency generator 17,preferably, a third RC circuit 25 provided with two different resistorsand diodes allocated respectively as is shown in FIG. 4 is used.

However, the exemplary circuits for ramp generators illustrated in FIGS.2 through 4 are background art and are only intended to explain thedesign of the variants according to the present invention and toindicate to one skilled in the art how the desired ramp function can bederived therefrom. In FIGS. 2 through 4, in particular, theconducting-state voltage of approximately 0.6 Volts of the diodes is nottaken into account.

In the discussed example, altogether, the typical duration of theincrease in the high-frequency power during the change from a depositionstep to an etching step lies at 0.2 to 5 sec, in particular, 0.5 sec to3 sec. Compared to that, the duration of the decrease in thehigh-frequency power during the change from an etching step to adeposition or polymerization step is markedly shorter and lies between 0sec to 2 sec, in particular 0 sec to 0.5 sec.

List of Reference Numerals  5 plasma etching system 10 substrate 11substrate electrode 12 substrate voltage generator 13 plasma source 14plasma 15 reactor 16 impedance transformer 17 high-frequency generator18 component 19 ramp generator 23 first RC circuit 24 second RC circuit25 third RC circuit

What is claimed is:
 1. A device for etching a patterned silicon bodysubstrate with a plasma, comprising: a high-frequency generator; aplasma source for generating a high-frequency electromagneticalternating field, a high frequency power to be applied to the plasmasource with assistance of the high-frequency generator; a reactor forgenerating the plasma from reactive particles through an action of thehigh-frequency electromagnetic alternating field upon one of a reactivegas and a reactive gas mixture; and a first arrangement for producing aperiodical change in the high-frequency power applied to the plasmasource; wherein the first arrangement includes one of: a component forcontrolling a power of the high-frequency generator, a digital rampgenerator being programed via a software in the component, and acomponent for controlling the power of the high-frequency generatorincluding an analog ramp generator.
 2. The device according to claim 1,wherein the analog ramp generator has an RC circuit which is providedwith at least one diode.
 3. The device according to claim 1, furthercomprising a second arrangement which, during the periodical change inthe high-frequency power applied to the plasma source, at leasttemporarily adapts an output impedance of the high-frequency generatorto a prevailing impedance of the plasma source which changes as afunction of the high-frequency power.
 4. The device according to claim3, wherein: the adaptation of the output impedance is carried out one ofcontinuously and stepwise and is automated; and the appliedhigh-frequency power lies between 400 W and 5000 W.
 5. The deviceaccording to claim 3, wherein the second arrangement is an impedancetransformer.
 6. A method for anisotropically etching a substrate using adevice for etching the substrate with a plasma, comprising the steps of:causing a plasma source to generate a high-frequency electromagneticalternating field, a high-frequency generator being adapted to apply ahigh-frequency power to the plasma source; causing a reactor to generatethe plasma from reactive particles through an action of thehigh-frequency electromagnetic alternating field upon one of a reactivegas and a reactive gas mixture; causing a first arrangement to produce aperiodical change in the high-frequency power applied to the plasmasource by one of: operating a component for controlling a power of thehigh-frequency generator via a software-programmed digital rampgenerator, and operating a component including an analog ramp generatorand for controlling the power of the high-frequency generator, carryingout the anisotropic etching process in separate etching andpolymerization steps alternatingly following each other; and applying apolymer to lateral patterns defined by an etching mask during thepolymerization steps, the polymer being removed again in each caseduring the subsequent etching steps; wherein, during the etching steps,at least temporarily, and in each case higher high-frequency power isapplied to the plasma source than during the deposition steps.
 7. Themethod according to claim 6, wherein during the etching steps, at leasttemporarily, a high-frequency power of 800 watts to 5000 watts isapplied to the plasma source, and during the deposition steps, at leasttemporarily, a high-frequency power of 400 watts to 1500 watts isapplied to the plasma source.
 8. The method according to claim 6,wherein at least one of: an increase in the high-frequency power duringa change from the deposition steps to the etching steps is carried outone of stepwise and continuously; and a decrease in the high-frequencypower during the change from the etching steps to the deposition stepsis carried out one of stepwise and continuously.
 9. The method accordingto claim 8, wherein at least the increase in the high-frequency power iscarried out in such a manner that during this time, at leasttemporarily, an impedance of the high-frequency generator is adapted toa plasma impedance at least approximately in (a) one of a continuous andstepwise, and (b) an automated manner via a second arrangement.
 10. Themethod according to claim 8, wherein at least one of: a duration of theincrease in the high-frequency power during the change from thedeposition steps to the etching steps is 0.2 sec to 5 sec; and aduration of the decrease increase in the high-frequency power during thechange from the etching steps to the deposition steps is 0 sec to 2 sec.11. The method according to claim 7, wherein during the etching stepsthe high-frequency power is between 2000 watts and 4000 watts.
 12. Themethod according to claim 7, wherein during the deposition steps thehigh-frequency power is between 500 watts to 1000 watts.
 13. The methodaccording to claim 9, wherein the second arrangement includes animpedance transformer.
 14. The method according to claim 10, wherein theduration of the increase in the high-frequency power during the changefrom the deposition steps to the etching steps is 0.5 sec to 3 sec. 15.The method according to claim 10, wherein the duration of the decreasein the high-frequency power during the change from the etching steps tothe deposition steps is 0 sec to 0.5 sec.
 16. A device for etching asubstrate with a plasma, comprising: a plasma source adapted to generatea high-frequency electromagnetic alternating field; a high-frequencygenerator adapted to apply a high-frequency power to the plasma source;a reactor adapted to generate the plasma from reactive particles by thehigh-frequency electromagnetic alternating field acting on one of areactive gas and a reactive gas mixture; and a first arrangement adaptedto produce a periodical change in the high-frequency power applied tothe plasma source, the first arrangement being a component forcontrolling a power of the high-frequency generator, the componentincluding one of a digital ramp generator programmed via a software andan analog ramp generator.